In architecture, detail is everything: the curves and outlines of the almost rhomboid cupola surpass all other silhouettes of its kind, even that of Brunelleschi's cupola for the Duomo in Florence and those of the great mosques of Istanbul and Cairo. If one views the dome of Saint Peter's from the south or west, whence the weaknesses of later architects are not apparent, its impact, the testament of the aged Michelangelo, makes one wonder what the secret of this dome can be. Theoretically, it should not have been difficult to design. In fact only one man was capable of devising it, and granted the inspiration to carry it out. In harmonizing elements which are eternally and fundamentally opposed, his genius drew upon the accumulated wisdom of his life. The pointed cupola reveals the mystery of the universe; the miracle of reconciliation between God and man. Shining above the Eternal City, the silver-grey dome radiates love. Michelangelo projected a dome in a slightly pointed form, and this was the shape adopted by the builders. As with Brunelleschi's Florence dome, the pointed shape exerts less thrust, and it was this which was decisive when, between 1585 and 1590, it was built by Giacomo della Porta with the assistance of Domenico Fontana, who was probably the best engineer of the day. Source: www.kfki.hu/~arthp/html/m/michelan/5archite/late/3spietr3.html